Doozle, called Kuro in Japanese-language media, is a black dog with distinct white patches on his snout, tail, and paws. He lives on Third Street with his owner, Yasushi Mikawa, who runs the local supermarket. Bursting with high energy and athleticism, Doozle loves running and physical exercise purely for fun. His kind-hearted nature and strong sense of justice drive him to act as the neighborhood's unofficial watchdog. He investigates minor local troubles like theft or property damage. In one documented instance, he intervened to help another character suffering distress from catnip exposure, showcasing his protective instincts.

Doozle shares a close companionship with Gon, another dog living on Third Street. The two are nearly inseparable, consistently appearing together across various media. While generally capable, he sometimes displays clumsiness during activities. In anthropomorphic narrative portrayals, Doozle retains distinctly canine traits, exhibiting heightened physical movement and investigative curiosity through scent. His narrative function centers on providing energetic support during group endeavors and reinforcing themes of communal responsibility through his self-appointed patrol of Third Street's safety.